Multi-phase industrial electrical power distribution systems are protected against damage from overcurrent circuit conditions by corresponding multi-pole circuit breakers wherein each phase of the power distribution circuit is directed through a separate pole within the circuit breaker assembly.
One of the problems encountered in the design and manufacture of a multi-pole circuit breaker is the provision of a pair of operating springs of sufficient strength to open and close each pole simultaneously when turning the circuit breaker contacts between their open and closed positions. U.S. Pat. No. 4,090,157 entitled "Operating Handle Means for Stacked Circuit Breaker Modules" proposes the use of a separate operating spring within each separate pole of a multi-pole circuit breaker arrangement. U.S. Pat. No. 4,736,174 describes a pair of operating springs used within the center pole of a three-pole circuit breaker to separate the circuit breaker contacts within each individual pole during overcurrent conditions as well during manual opening and closing of the circuit breaker contacts.
In some industrial electrical power distribution systems, four-pole circuit breakers are installed to protect the electrical circuit as well as the associated industrial equipment. The movable contact arms which carry the movable contacts within the separate poles are, in turn, carried by a common unitary crossbar assembly. The provision of such a four-pole circuit breaker requires a unitary crossbar assembly of increased length. The addition of a fourth pole to a standard three-pole circuit breaker design increases the static coefficients of friction associated with the pivot pins that rotatably carry the movable contact arms and hence requires larger operating springs to overcome the increased friction.
It would be economically advantageous to provide a four-pole circuit breaker capable of separating the contacts within the separate poles without requiring a larger pair of operating springs than a three-pole circuit breaker or a longer crossbar assembly. It would be further advantageous to provide a modular crossbar unit that could be additively combined to form multi-pole circuit breakers without requiring a separate crossbar assembly for each multi-pole design.
One purpose of the invention is to provide a modular crossbar arrangement whereby a plurality of circuit breaker poles can be fabricated from a common modular crossbar unit.
A further purpose of the invention is to provide a contact arm accelerator lever to increase the closing force applied to the movable contact arms within a standard multi-pole circuit breaker design.
An additional purpose of the invention is to provide means for decreasing the effects of friction on the movable contact arms in existing multi-pole circuit breaker designs.